#define _CRT_SECURE_NO_WARNINGS 1
//1 1 2 3 5 8
#include<stdio.h>
int fib(int n)
{
	if (n == 1)
	{
		return 1;
	}
	else if (n == 2)
	{
		return 1;
	}
	else
	{
		return fib(n - 2) + fib(n -1);
	}
}
int main()
{
	int n = 0;
	scanf("%d", &n);
	int ret = fib(n);
	printf("ret=%d", ret);
	return 0;
}